The goal of this application is to understand how related GATA transcription factors elicit distinct transcriptional responses during the regulation of hematopoietic genes. GATA-1 and GATA-2 control different aspects of blood cell development yet possess highly conserved DNA binding and protein interaction domains. The following Specific Aims will address GATA factor specificity and function in erythroid cells. Aim 1. To determine how GATA-1 and GATA-2 elicit similar and distinct transcriptional responses. The zinc fingers of GATA factors are crucial for function and are well conserved among GATA family members. The contribution of non-finger sequences to GATA function is unclear but these sequences may confer GATA factor-specific functions, potentially in a context dependant manner. A structure-function analysis of GATA-1 and GATA-2 will define sequence requirements for the regulation of GATA target genes in primitive and definitive erythrocytes. Non-finger sequences will also be analyzed for involvement in protein-protein interactions with the intent of identifying novel GATA-1 interactors. Aim 2. To define the requirements for GATA-1 binding to sites in the Beta-globin locus. At the endogenous murine Beta-globin locus, GATA-1 binding in definitive erythroid cell lines is restricted to a subset of the available sites residing in regions of high histone acetylation. To determine if chromatin structure underlies the restricted pattern of GATA-1 binding in the Beta-globin locus, GATA-1 binding will be analyzed at the locus in primitive erythrocytes which exhibits a broader distribution of histone acetylation. The role of the Beta-globin locus control region (LCR) in GATA-1 binding at the Beta-globin promoters will also be ascertained through the use of murine ES cells containing a deletion of the LCR. The proposed studies will advance work done by the candidate in the laboratory of Dr Emery Bresnick but represent a more comprehensive approach for investigating GATA factor function.